Screw-jack



UNITE il@ HENRY F. SHAV, OF SOUTH BOSTON, MASSACHUSETTS.

SCREW-JACK.

Specification of Letters Patent No.

To all whom t may concern.'

Be it known that I, H. F. SHAW, of South Boston, in the county of Suffolk and State of Massachusetts, have invented a new and Improved Screw-J ack, of which the following is a full, clear, and exact description, reference being had to the annexed drawings, making part of this specification, in which- Figure l is a view of the jack; Fig. 2, a section upon the line A, A, of Fig. l.

To enable others skilled in the art to understand my invention, I will proceed to describe the manner in which I have carried it out.

In the accompanying drawings, B, is the body of the jack, in the opposite ends of which work the screws C. The heads of these screws are pointed or convex, and rest in the center of the plates E, one of which is placed upon the ground, or other support, and the other beneath the body to be raised.

Gr are double pawls, one or other of the teeth of which may be brought to bear upon the ratchet wheel D, near the head of the screws. These pawls may be shifted at any instant so as to change the operation of the screws in order gradually to raise or lower the body as may be required.

IVith the parts constructed and arranged as above described, it is simply necessary to vibrate the body of the jack B, by means of a lever entered at the hole I-I, in order to op- 14,170, dated January 29, 1856.

erate both the screws simultaneously. This jack it is evident may be operated in confined positions where it would not be possible to move the levers a sufficient distance to operate an ordinary screw jack, a slight vibration of the levers only being necessary.

In order to lower the body gradually, it is simply necessary to shift the pawls when by the continued operation of the levers the motion of the screws is reversed and the body is lowered as desired. One or other of the teeth of the pawl g, is caused to operate upon the ratchet teeth D, by the spring 7L. If one of these teeth be brought into action, then the screw will be allowed to move in one direction but not in the other, and the body will be raised. If the other tooth of the pawl be thrown into action upon the teeth D, the screw will be moved in a contrary direction only, and the weight or body resting upon the jack will be lowered. The

screws C, are both right hand screws, their heads turn freely upon the plates F.

I/Vhat I claim as my invention and desire to secure by Letters Patent is The within described screw jack consisting essentially of the screws C, plates E, and 

